The access server receives an authentication packet including an authentication result, a port change setting information, a port change time, a filtering setting information and a filtering time from the authentication server. The access server stores the respective information in the authentication packet into a memory. The access server refers to the memory, and in the case where the port change setting information on an arbitrary user identifier is set to perform port change, when it becomes the port change time, the access server changes the output destination of a packet from a user terminal to, for example, a proxy server B from a proxy server A. Besides, in the case where the filtering setting information on an arbitrary user identifier is set to perform filtering, when it becomes the filtering start time, the access server performs filtering on the port to which the user terminal is connected.